Method for obtaining fluid samples from drilled wells



Feb. 16, 1937. G A, A READY 2,070,836

METHOD FOR OBTAINING FLUID SAMPLES FROM DRILLED WELLS Filed Oct. 1, 1935la "zil m a Fig. 1.

Patented Feb. 16, 1937 UNITED STATES METHOD FOR OBTAINING FLUID SAMPLESFROM DRILLED WELLS George A. Macready, Los Angeles, Calif.

Application October 1, 1935, Serial N0. 43,074

2 Claims.

My invention relates to bore holes or drilled wells in which it isdesired to test formations penetrated by the drill to determine thecharacter of fluid the formation may yield.

In the art of drilling wells for petroleum or other fluid products it isessential that undesirable fluid such as water be excluded from theproductive formations. The usual practice is to seal a string of steelcasing to the wall of the well by cement so that all fluid originatingfrom formations above the seal is excluded from the interior of thecasing and the desired fluid from formations below the seal can then bedrawn to the surface through the casing.

Wells drilled by hydraulic methods are kept full of mud laden drillingfluid so that it is difficult to identify the character of fluid aformation penetrated may yield. Casing is expensive so that it isdesirable to make a preliminary test of the formation before permanentlycementing casing. The test can be made by taking a sample of fluid by mymethod.

In 1922 I invented a method and apparatus by which a sample of fluidcould be caused to enter and become entrapped in drill pipe and broughtto the surface in the pipe for inspection, and was granted Patents1,896,492 and 1,896,522 therefor. Other inventors have followed withimprovements thereon.

It requires sometimes several hours to bring the sample to the surfaceby pulling it out in the drill pipe. My present invention provides forboosting the sample up through the drill pipe to the surface forinspection before pulling the drill pipe. Considerable time is savedthereby so that the well operator can decide on the next procedure forhis well while the drill pipe is being pulled from the well.

An object of my invention is to provide a method for obtaining fluidsamples from drilled wells by inserting a tube into a well, temporarilysealing the tube against the wall of the well to exclude fluid in thewell above the seal from entering the interior of the tube, causing asample of fluid from below the seal to enter the tube, breaking theseal, and pumping a measured quantity of liquid into the well outsidethe tube sufflcient to displace the sample upwardly through the tube todischarge from the top of the well for inspection.

With the foregoing and other objects in view which will be made manifestin the following detailed description and especially pointed out in theappended claims, reference is had to the accompanying drawing forillustrative embodiment of my invention, wherein:

Figure 1 is a longitudinal section of a well showing a sample tubetherein with a sample of formation fluid drawn into the tube and a pumpwith fluid measuring apparatus shown in elevation at the ground surface,and

Figure 2. is a longitudinal section of a well showing the sample tuberaised to break its seal and the sample of formation fluid displaced tothe ground surface for inspection.

Similar numerals refer to similar parts throughout the several-views.

My method is for determining the character of formation fluid F thatwill be yielded by a formation T encountered in a well as illustrated onFigures 1 and 2. A tube I is inserted into the well and sealed againstthe wall of the well as at S by means of a packer P.

The tube I may be the conventional casing, tubing or drill rod used inwell practice such as the drill pipe used in drilling the well. Thepacker illustrated at P is of the rat hole type which makes a seal bybeing pressed by weight of the drill pipe imposed upon it against apreviously formed shoulder on the well wall. The seal forms an annularbarrier around tube I so that fluid cannot flow up or down outside thetube past the barrier. This application for Letters Patent is notdirected to the specific form of seal and any other conventional type ofpacker can be selected to be most eificient for the individual well,such.- as a flush wall formation packer, or a hook wall casing packer ifthe seal is made against casing.

After the seal S has been made to exclude overlying fluid a sample offormation fluid F from formation T is next caused to enter tube I.

The sample F may be caused to enter tube l by any of several proceduresamong them being the following: I

(a) Drilling fluid in tube I may be removed therefrom by pumping,swabbing or bailing, cap

I6 being removed, until the hydrostatic pressure within tube I is lessthan the pressure in forma tion T which causes the sample of fluid F toflow through inlet 2 into tube I.

(b) Using the apparatus illustrated in applicants Patent Number1,896,522 the drilling fluid in tube I can be expelled by admittingcompressed gas through valve 3 to express the drilling fluid M through aside check valve illustrated at 4 or through the inlet 2 if the -airpressure has been applied during lowering of tube I before making sealS. After the seal S has been made the compressed gas is released, asthrough valve 5 reducing the hydrostatic pressure in tube I so that asample of formation fluid F is caused to enter tube I through inlet 2.

(c) The valved packer apparatus illustrated in Patent Number 1,683,031granted to W. 0. Harris can be used and the tube I lowered into the wellIibf Harris the valve I8 of Harris is opened by matured into PatentNumber 2,040,619, granted May 12, 1936, can also be used to perform themethod described and claimed herein but not described in saidapplication.

After it is believed sufiicient sample of formation fluid F hastenteredtube I (illustrated on Figure 1), the seal S is broken by raising tube Ito lift packer P oifits seat.

Drilling mud M from .outside the tube rushes into tube I through inlet 2displacing sample F bodily upward in the tube I. Additional mud fluid M'is flowed or pumped into the top of the well as at 6. Thesample Fusually consists of water, oil or gas of lighter specific gravity thanthe mud drilling fluid M .or M so that when hydrostatic equilibrium isestablished the fluid level stands higher inside tube I than outsidetube I. It is common practice in oil well drilling to use drilling mudsof different specific gravities.

- By filling the well hole outside tube I to the surface with drillingfluid M of heavy specific gravity all-of the fluid originally in tube Iincluding sample F is displaced upwardly to discharge from the top ofthe well, as into vat I. v (Illustrated on Figure 2.)

For most efflcient use of my method the quantity of additional mud fluidM' supplied into the top of the well may be the same as the volume offluid that can be contained in tube I, which is readily computed fromthe known dimensions of tube I. When this known quantity of mud fluid Mhas been supplied into the well then it is known that the sample offormation fluid F has been completely displaced from tube I to dischargeat the top of the well.

The quantity of mud fluid M may be measured by any of numerous standardmethods, four of which are illustrated on Figure 1 as follows, althoughonly one measuring method is sumcient:

(a) The quantity of fluid M supplied into the top of the well can bemeasured by pumping with.

pump II through suction I4 from vats 8, 9 of known calibration.

(b) The quantity of fluid M' can be measured by a liquid meter III inthe supply line registering on scale I64.

(c) The qauntity of fluid M can be measured by counting the strokes ofpump II either mentally or by a mechanical counter I2 registering onscale I63, the delivery capacity of each stroke having been previouslycalibrated.

(d) The quantity of fluid M' can be estimated mentally by an expertoperator.

The following auxiliary conditions and precautions improve efliciency.

The inlet 2 should be selected of such small diameter that the maximumrate of flow through it with its greatest pressure differential shouldnot be greater than the flow of liquid that pump I I is capable ofsupplying so that there may be no danger of the fluid level in the wellfalling to the danger point to cause a blow out.

To protect inlet 2 from clogging with dbris a perforated tube I3 may beused.

During the period that mud fluid M' is being supplied to the well the.tube I may be moved vertically or rotated to prevent its sticking inthe well.

In the event that it is impractical or inconvenlent to use mud ofdifferent specific gravities a aoraesc packing gland of any conventionaltype can be inserted between tube I and the wall of the well near itstop so as to prevent leakage, and the mud fluid M forced into the top ofthe well under pressure.

It is advisable to select the level for seal S at a depth where theformation or wall of the well is impervious and has suflicient strengthto support the hydrostatic load on the seal.

The vertical distance of outlet I5 above the top of the well should beat a minimum to facilitate complete discharge of'sample F.

In deep wells a pressure relief valve may be used on the packer tolessen the strain of lifting the packer off its seat.

After the sample F has been displaced to the surface for inspection thedirection of flow of mud fluid in tube I may be reversed if desirableand the tube I removed from the well.

displaced to the surface, can be inspected to determine its characterand value and the probable yield to be expected from formation T.

The operator of the well then has suflicient time to decide on the nextprocedure for his well while the tube I is being withdrawn from thewell.

Where secrecy is desired against prying speculators the sample F may bedischarged into a closed tank to be inspected only by the operator orhis agents and friends.

I claim as my invention:

1. A method of obtaining fluid samples from wells which consists ofinserting a tube into a well, temporarily sealing the tube against thewall of the well to exclude fluid in the well above the seal fromentering the interior of the tube,

causing a sample of fluid from below the seal to enter the tube,breaking the temporary seal, supplying a measured quantity of liquidinto the well outside the tube sufiicient to displace said sampleupwardly through the .tube to discharge from the top of the tube forinspection and identifying .as the sample that fluid which hasdischarged from the top of the well when the quantity of liquid suppliedoutside the tube is substantially equal to the interior cubic volume ofsaid tube.

2. A method of obtaining fluid samples from wells which consists ofinserting 'a tube-into a well, temporarily sealing the tube against thewall of the well to exclude fluid in the well above the seal fromentering the interior of the tube, causing a sample of fluid from belowthe seal to enter the tube, breaking the temporary seal, supplying aquantity of liquid into the well outside the tube substantially equal tothe interior cubic volume of said tube so as to displace said sampleupwardly through said tube to discharge from the top of said tube forinspection and identifying as the sample that fluid which has dischargedwhen said quantity has filled the well outside aid tube.

GEORGE A. MACREADY.

